Synthesis of salmon calcitonin

ABSTRACT

Resin peptides useful in the preparation of salmon calcitonin are disclosed along with processes for preparing the same. The invention also embraces peptides from which the resin moiety has been cleaved and which are useful in the synthesis of salmon calcitonin together with processes for preparing the cleaved peptides. In general, the processes involve the solid phase synthesis procedures. The invention deals with new compounds containing an amino acid chain similar to that of salmon calcitonin and new methods for closing the ring structure in such compounds to produce calcitonin.

' Unite States atent [191 Hughes et al.

[ Dec. 16, 1975 SYNTHESIS OF SALMON CALCITONIN Inventors: John Lawrence Hughes, Kankakee;

Jay Kenneth Seyler, Bourbonnais; Robert Chung-Huang Liu, Kankakee, all of I11.

Armour Pharmaceutical Company, Phoenix, Ariz.

Filed: Aug. 12, 1974 Appl. No.: 496,539

Assignee:

Foreign Application Priority Data Dec. 7, 1972 US. Cl. 260/112.5 Int. Cl. C07C 103/52; CO7G 7/00 Field of Search 260/ 1 12.5

References Cited UNlTED STATES PATENTS 4/1974 Guttmann et al 260/1125 11/1974 Rittel et a1. 260/1125 Japan 47-121973 OTHER PUBLICATIONS Hagenmaier et al., Chem. Abstr., 79; 92564u, (1973). I

Primary ExaminerLewis Gotts Assistant ExaminerReginald J. Suyat Attorney, Agent, or FirmRichard R. Mybeck; Carl C. Batz [57] ABSTRACT tides. In general, the processes involve the solid phase synthesis procedures.

The invention deals with new compounds containing an amino acid chain similar to that of salmon calcitonin and new methods for closing the ring structure in such compounds to produce calcitonin.

23 Claims, No Drawings calcitonin by such addition has not heretofore been SYNTHESIS OF SALMON CALCITONIN reported.

This invention relates to the hormone calcitonin and DESCRIPTION OF INVENTION to substances having biological activity similar to calci- In general we use a solid phase type of synthesis and tonin and to substances which may be converted into start with a resin called benzhydryl amine resin (Bl-1A such biologically active substances. The invention deals resin). This resin is derived from a cross-linked polystyalso with processes for the preparation of these subrene bead resin manufactured by copolymerization of stances. styrene and divinylbenzene. Resin of this type is known BACKGROUND and its preparation is further demonstrated by Pletta et 4 al (Pietta, P. S. and Marshall, G. R., Chem. Commun., It is known that biological substances of natural ori- 650 [1970]). This cross-linked polystyrene BHA resin gin can be obtained from the glands of land and aquatic is available from chemical supply houses. We use the animals and that such substances can be used to treat designation hormonal deficiencies in man and other animals. Among such substances is the hormone calcitonin. This hormone has been found to be particularly useful in the i treatment of Pagets Disease (See the article by DeRose et al entitled Treatment of Pagets Disease with Calcitonin in Seminars in Drug Treatment, Vol. to represent the BHA resin in which@ 2, No. 1 [summer, 1972] is the polystyrene portion of the resin.

Calcitonins have been obtained from bovine, porcine and human sources and these have been found'to ex-. hibit hormonal action when administered to animals or In this synthesis the amino acids are added one at a to man. The most active of the calcit i has bee 5 time to the insoluble resin until the total peptide seobtained from salmon fishes. (Copp, D.H. Parkes, quence has been built up on the resin. The functional CO, and ODor, R.K., Feder. Proc. 28/2, 413 [1969]). groups of the amino acids are protected by blocking The calcitonin extract obtained from salmon has been groups The -amino group of the amino acids is propui'ified (Keutmann, H.T., et al., J. Biol. Chem, 245, tected by a tertiary butyloxycarbonyl group or an 1491-6 [1970]) and it structure el idat d (Ni ll, equivalent thereof. The a-tertiary butyloxycarbonyl H.D., et. al., Proc. Nat. Acad. Sci 64, 771-8 [1969]). group we designate as BOC. The hydroxyl functions of The material was found to be a 32 amino acid carboxyl serine and threonine are protected by a benzyl or benterminal amide peptide containing a disulfide bridge zyl derivative group Such as 4-methoxybenzyl, 4-methbetween the cysteine moieties at positions'l and 7. ylbenzyl, 3,4-dimethyl b n y 4- hlor y Using the abbreviations CYS, SER, ASN, etc. t repredichlorobenzyl, 4-nitrobenzyl, benzhydryl or an equivsent the amino acid residues, the formula for salmon alent thereof. We use the term 32 to represent benzyl Resin Peptide Synthesis calcitonin may be written as follows; or benzyl derivative group. The hydroxyl function of H,N-Ci (S-S R-A N-L u-s R-THR--C S-VALL U-G Y-LTS-Ll|'-IU-SliR-Gl[N-Gll.U i I I T I i I i I 1i; 11 12 13 14 15 NH, I Q O=PfO-THR-GTY-SlI=.R-GTY-THR-A NTHRARGPRO-TTRTTR-GTN-LliU-LTS-HIIS-LT.U 3 31 30 29 28 2'7 is 2'5 24 23 22 21 2o 19 1s 17 16 tyrosine may be unprotected, may be protected by a The burden of routinely collecting the small ultimobenzyl or benzyl derivative group as described above, branchial gland of salmon from which calcitonin is as a BZ group, or may be protected by a benzyloxycarobtained, the low yield of active extract obtained, and bonyl or a benzyloxycarbonyl derivative such as a 2- the small and rapidly diminishing size of the salmon chlorobenzyloxycarbonyl or a 2-bromobenzyloxycarcatch, produce supply problems which cry out for a bonyl group or equivalent thereof. We use the term W practical method for the synthesis of salmon calcitonin, to represent either no protective group, a 132 group, a or for the synthesis of substances not heretofore known benzyloxycarbonyl group or a benzyloxycarbonyl dewhich can be converted to substances having calcitonin rivative group. The thiol function of cysteine may be hormonal activity. We have therefore set about to disprotected by benzyl or benzyl derivative protective cover such methods and substances. groups described above and designated 82 or by an Although the synthesis of salmon calcitonin using n-alkylthio group such as methylthio, ethylthio, nproclassical peptide synthesis has been reported (Guttpylthio, n-butylthio or equivalents thereof. We use the mann, S., et.al., Helv. Chim. Acta 52, 1789-1795 character R to represent the n=alkylthio groups or the [1969]), the art has been seeking processes which 132 groups on cysteine. The guanidino function of argiwould be more practical for larger scale commercial nine may be protected by a nitro group, a tosyl group or production. Although methods are known for the synan equivalent thereof. We use the character T to repre thesis of certain peptides by addition of amino acids sent either a nitro group or a tosyl group. The eamino singularly, (Merrifield, R. B., J. Am. Chem. Soc, 85, function of lysine may be protected by a benzyloxyean 2149-64 [1963], and Pietta, P. S. and Marshall, G. R., bonyl group or a benzyloxycarbonyl derivative such as Chem. Commun., 650 [1970]) the synthesis of salmon Lchlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl, 3,4-dimethylbenzyloxycarbonyl or equivalents thereof. We use the character V to represent benzyloxy carbonyl group or a benzyloxycarbonyl derivative group. The protective groups used on the imidazole nitrogen of histidine are the benzyloxycarbonyl group and benzyloxycarbonyl derivatives such as described above for lysine and are designated as V. The y-carboxylic acid group of glutamic acid is protected by a benzyl or benzyl derivative group such as described for the protection of the hydroxyl function of serine and threonine. These protective groups are represented by the character BZ.

As may be seen from the formula of salmon calcitonin above given, 32 amino acids are involved and in this formula the positions are numbered according to the accepted custom beginning at position 1 for the CYS on one end of the chain and ending with PRO at position 32 at the other end of the chain. For clarity of description this same numbering system will be followed in referring to the cycles of the synthesis. The assembly of the amino acids begins with cycle 32 which involves the coupling of proline and continues with cycle 31 which involves the coupling of threonine, etc.

Preferred amino acid reactants for use in each of the 32 cycles of the synthesis are given in the following Table I:

TABLE 1 Amino Acid Reactant BOC-Lproline BOC-O-benzyl-L-threonin BOC-glycine BOC-O-benzyl-L-se rine BOC-glycine BOC-O-benzyl-L-threonine BOC-L-asparagine p-nitrophenyl ester BOC-O-benzyl-L-threonine BOC-Qmitro-L-arginine or BOC-Q-tosyl-L-arginine BOC-L-proline BOC-O-benzyl-L-tyrosine. BOC-L- tyrosine. or BOC-O-Z- bromobenzyloxycarbonyl-L- tyrosine BOC-O-benzyl-L-threonine BOC-L-glutamine p-nitrophenyl ester BOC-L-leucine BOC-e-CBZ-L-lysine or BOC-e-Z- chlorobenzyloxycarbonyl-L-lysine BOC-N( im )-CBZ-L -histidine BOC-L-leucine BOC-L-glutamic acid 'y-benzyl ester BOC-L-glutamine p-nitrophenyl ester BOC-L-benzyl-L-serine BOC-L-leucine BOC-e-CBZ-L-lysine or BOC-e-Z- chlorobenzyloxycarbonyl-L-lysine BOG-glycine BOC-L-leucine BOC-L-valine BOC-S-ethylthio-bcysteine, BOC-S- methylthio-L-cysteine, BOC-S-npropylthio-L-cysteine or BOC-S- n-butylthio-L-cysteine BOC-O-benzyl-L-threonine BOC-O-benzyl-L-se rine BOC-L-leucine BOC-L-asparagine p-nitrophenyl ester BOC-O-benzyl-L-serine BOC-S-p-methoxybenzyl-L-cysteine. BOC-S- benzyl-L-cysteine or BOC-S-3.4- dimethylbenzyl-L-cysteine Each of the amino acid derivatives mentioned in Table I may be purchased from supply houses except 4- 7. These materials useful in cycle 7 may be prepared according to the method described in the literature (U. Wever and P. Hartter, Hoppe-Seylers, Z. Physio]. Chem. 351, 1384-8 [1970]).

CYCLE 32 Coupling of Proline to BHA Resin The reaction vessel used in all steps of the resin peptide synthesis may be a glass vessel equipped with inlet ports at the top for addition of materials and a sintered glass disk at the bottom for removal of soluble reaction mixtures and wash solvents by filtration. Filtration can be performed either by vacuum or the use of nitrogen pressure. The contents of the vessel can be agitated by shaking the entire vessel or by a mechanical stirrer.

In cycle 32 the BHA resin is placed in the reaction vessel and suspended in a solvent such as methylene chloride, chloroform, dimethylformamide, benzene or equivalents thereof in proportions of 3 to 12 ml of solvent per gram of resin. To this is added BOC-L-proline in an amount of l to 6 equivalents per free amine equivalent of the BHA resin employed. After a period of mixing of 5 to l0 minutes, a coupling reagent (CA) such as dicyclohexyl carbodiimide (DCC) is added. Other diimide coupling agents may be used. The diimide coupling agent is used in the amount of 0.5 to 2.0 equivalents per equivalent of BOC-L-proline used.

The BOC-L-proline may be coupled in the absence of a coupling reagent if its active ester derivative, its azide derivative, its symetrical anhydride derivative, or a suitably chosen mixed anhydride derivative is used. The active ester derivatives that may be employed are Z-nitrophenyl ester, 4-nitrophenyl ester, pentafluorophenyl ester, N-hydroxysuccimide ester or equivalents thereof. The active esters are used in amounts of l to 10 equivalents per free amine equivalent of BHA resin.

The reaction mixture consisting of the BHA resin, the solvent, the BOC-L-proline, and the coupling reagent or BOC-L-proline active ester is stirred or shaken mechanically until the reaction is complete as is indicated by a ninhydrin test (E. Kaiser, et. al., Anal. Biochem., 34 595-8 [1970]) on a test sample. After completion of the coupling reaction, the BOC-L-proline resin may be washed with solvents such as methylene chloride, chloroform, methyl alcohol, benzene, dimethylformamide, or acetic acid. The amount of wash solvent may suitably be 2 to 20 ml of solvent for each gram of BHA resin used initially. If it is desired to terminate the coupling reaction before completion, the washing procedure is used and the remaining free amino groups on the BOC-L-proline resin may be blocked from further reaction by acetylation with an excess of acetylation reagents. The acetylation procedure is performed by agitating the BOC-L-proline resin with a solution of the acetylation reagent for a period of 0.5 to 12 hours. Acetylation reagents such as N-acetylimidazole in methylene chloride solution or a mixture of acetic anhydride and triethylamine in chloroform can be used. The acetylation reagent may be used in the amount of 0.5 to 5.0 equivalents per equivalent of free amine titer of the starting BHA resin.

The coupling reaction to produce the BOC-L-proline perhaps the derivative mentioned for use in cycle N0. resin may be described by the following formula:

The "BOC-L-proline resin produced as above described may be washed with a solvent such as referred to above and deprotected by agitating it with an agent such as a mixture of trifluoroacetic acid (TFA) in a solvent such as methylene chloride, chlorofonn, ben- 15 zene or equivalents thereof The amount of TFA in the solvent can vary from 10 to 100% of the mixture. The amount of TFA-solvent mixture may vary from 3 to 20 ml per gram of BHA resin used initially. The reaction time may be from about 10 minutesto 4 hours. The 20 of triethylamine in a solvent such as methylene chlo- 25 ride, chloroform, benzene or equivalents thereof.

CHO 6 5 u Other tertiary or secondary organic amines may be used in place of the triethyl amine such as trimethylamine, N-ethylpiperidine, diisopropylamine or equivalents thereof. The free amine titer of the L-proline resin may be determined by the Dorrnan titration procedure 55 (Dorman, L.C., Tetrahedron Letters, 1969 2319-21). The deprotection reaction may be described by the following formula:

6 5 n 1 TFA l (CH C-O c H O C H vO l (CH c0 OC(CH3,) v 3 3 Deprotection of BOC-L-proline Resin l0 CYCLE 31 The prolyl BHA resin obtained as a result of cycle 32 may be suspended in a coupling solvent, the BOC-O- BZ-L-threonine derivative added and the mixture equilibrated in the same manner. The coupling agent, DCC, may' be added and after completion of the reaction as indicated by the ninhydrin test, the reaction mixture is removed from the BOC-O-BZ-threonylprolyl BZ I DCC

3 3 coon l 1 TFA 2) N c n COfiINHFH 0 eucn OBZ For convenience, we may write this resulting resin peptide using abbreviated nomenclature as follows:

CYCLE 30 In cycle 30 the coupling reaction and also the deprotection reaction may be performed in the same manner as in cycle 31 except that BOC-glycine is used in place of BOC-O-BZ-L-threonine. The reaction through coupling and deprotection may be written:

This compound, to our knowledge, has never been reported and as will later be shown may be converted to salmon calcitonin.

CYCLE 29 In cycle 29 the coupling and deprotection reactions 20 8 CYCLE 26 In cycle 26 the coupling reaction is performed using an active ester derivative of BOC-L-asparagine. The active ester procedure is used in place of the DCC coupling method to avoid a known side reaction that occurs with the use of DCC coupling agent with BOC- asparagine or BOC-glutamine. The reaction is performed using the active ester derivative of BOC-L- asparagine in the amount of 2 to 10 equivalents per free amine equivalent of BHA resin in dimethylformamide, mixtures of dimethylformamide with benzene, methylene chloride or chloroform or with equivalents thereof in amounts of 2 to 20 ml of solvent per gram of BHA resin used initially. Reaction times are from 1 to 72 hours. The reaction mixture is removed from the BOC- peptide resin by filtration after completion of the reaction as indicated by a ninhydrin test. The active esters derivative employed may be 2-nitrophenyl esters, 4- nitrophenyl esters, pentafluorophenyl, or equivalents thereof. We use AE to designate the active ester portion of the derivative. The coupling reaction may be written:

CYCLE 28 In cycle 28 the coupling and deprotection reactions are performed as described in cycle 31 except that BOC-glycine is substituted as the amino acid reactant. These reactions through coupling and deprotection The deprotection reaction to remove the BOC group is performed as in cycle 32.

CYCLES 25 21 BZ Z may be written as follows:

C H BZ BZ CYCLE 20 In cycle 20 the coupling and deprotection reactions may be performed using the methods and proportions of reactants as in cycle 26 using a BOC-L-glutamine active ester derivative as the amino acid derivative, resulting in the compound:

BZ BZ T W BZ CYCLE 27 In this cycle the coupling and deprotection reactions may be as in cycle 31 using the same amino acid reactant, resulting in the following compound:

CYCLE19 ln cycle 19 the reactions are performed as in cycle 31 using BOC-L-leucine as the amino acid derivative. The compound resulting from cycle 19 is:

BZ 82 T W 82 CYCLE 18 In cycle 18 we may use as the amino acid derivative BOC-e-V-L-lysine. Otherwise, cycle 18 methods may be performed as in cycle 31 resulting in the compound:

derivative. The compounds resulting from cycle 7 are described by the formula:

LEU-LYS-NH CYCLES 17- 15 Cycles 17 to 15 may be performed as in cycle 31 except for the use ofBOC-N(im)-V-L-histidine in cycle 17, BOC-L-leucine as the reactant in cycle 16 and BOC-L-glutamic acid BZ ester (BZ represents the same groups as it represents for serine and threonine) as the reactant in cycle 15, resulting in the following compound from cycle 15:

CYCLES 6 to 2 L \l/ v i2 LEU-LYS-HlS-LEU- LU-NH2 CYCLES 14 8 Cycle 14 may be performed identically to cycle 20 dures may be the same as cycle 31 using BOC-O-BZ-L- serine as the amino acid derivative. The compound resulting from cycle 2 is:

BZ BZ BZ T Z Z Z BZ I V ll V I I -.LEU-LYSHISLEU LU-GLN-SER-LEU-LiS-GLY-LEU-VAL-C S- HR-LERj LEU-ASN IER-NH CYCLE 1 This cycle may be performed identically to cycle 7 using BOC-S-R-L-cysteine derivatives. The R group chosen for the cysteine may be the, same as used in cycle 7 or different. For example, if the derivative chosen for cycle 7 is BOC-S-ethylthio-L-cysteine the derivative in cycle 1 may be BOC-S-4-methoxybenzyll I l i I GLN--LEUL S-H S-LEU- LU-GLN- ER-LEU-LYS-GLYLEUVAL--NH CYCLE 7 Cycle 7 may be performed as in cycle 31 except for the use of BOC-S-R-L-cysteine or for the amino acid L-cysteine or if BOC-S-4-methoxybenzyl-L-cysteine was chosen for cycle 7', then this derivative may be used also in cycle 1. The compounds resulting from cycle 1 are described 8; the formula:

C H B2 82 W Cycle 1 represents the completion of the salmon 10 cleavage procedure and remains intact throughout the calcitonin resin peptide. The resin peptide may be recleavage and extraction procedure. The S-BZ-L-cysmoved from the reaction vessel and dried in a vacuum. teine residue is cleaved by HF to yield a cysteine resi- The weight of the resin p p y be expected to be due with a free thiol function. Both types of blocking from t0 times the Weight of BHA resin Used groups have been employed during our synthesis either initially in the syhthesissingly or in combination with each other at positions 7 and 1. Thus, the peptides obtained after HF cleavage Resm Peptide Cleavage can be one of several types depending upon the block- The p p is cleaved from the resin p p Yesuhing groups chosen for the thiol function of the cysteine g from cycle 1 y treatment with liquid y g derivative used during the resin peptide synthesis. fluoride (HF). The HF cleavage reaction may be per- If BOC-S-BZ-L-cysteine derivatives were used in formed y treating a mixture of the resin P p and resin peptide synthesis cycles 7 and l, the peptide reahiSOle t0 5 ml for each g of resin p p sulting after HF cleavage should be of Type 1 and with liquid HF to 20 ml for each g of resin P P- would have free thiol functions at both cysteine resitide) fOI t0 hours at "20 to +15C. After the dues The peptide would be represented by the forreaction period the excess HF may be removed by mula;

evaporation and the resulting mixture of peptide and resin beads may be extracted with an organic solvent TYPE I PRO-THR-GLY-SER-GLY-THRASNTHRARG--PROTYRTHRGLNLEU NH such as ethyl acetate, diethyl ether, benzene or the like If y y derivatives were to remove the anisole and residual of HF. The peptide used in cycle 7 and the Y were may be separated from the resin beads by extraction 40 used in Position 1, the Peptide resulting from the cleavinto aqueous acetic acid. The peptide at this stage is not ag would be of the Type II and would be represented cyclic salmon calcitonin but is the non-cyclic product y the formula:

without the cyclic disulfide bond between the cysteines TYPE I] PRO-THR-GLY-SER-GLY-THR ASNTHRARG-PROTYR--THRGLNLEU L Snalkyl LYS-HIS-LEU-GLU-GLNSERLEU-LYS-GLY-LEU-VAL-C S-THR-SER at positions 1 and 7 in the molecule. If BOC-S-BZ-L-cysteine was used at position 7 and The HF treatment removes all blocking groups from BOC-S-n-alkylthio-L-cysteine was used at position 1, the peptide except in the materials that were-prepared the peptide resulting from HF cleavage would be a using the S-alkylthio blocking groups on the thio func- Type III peptide and is represented by the formula: tions of cysteine residues at either positions 7 or I. The TYPE III S-n-alkylthio-L-cysteine residue is stable to the HF LYS-HlS-LEU-GLU-GLN-SER-LEU-LYS-GLY-LEU-VAL-CYS-THR-SER-LEU- L S-S-n-alkyl ASN--SER -CiS-NH v Each of the three types above described can be converted to fully active salmon calcitonin by methods we will describe as follows.

Formation of Disulfi de Ring Structure The crude peptide solution obtained from the HF cleavage procedure may be converted to active salmon s NH2/ tion. The pH of the solution is lowered to 3 to 5 by addition of acetic acid. The peptide has now been converted to salmon calcitonin and can be purified. Other oxidizing agents may be used in place of atmospheric oxygen such as ferricyanide ion and diazene dicarboxylic acid (N,N-dimethyl amide). The reaction is illustrated below: I

Type I Peptide H2O pH 6.0-8.5

TYPE I PEPTIDE Type I peptide contains cysteine residues with free thiol groups. The disulfide ring closure is performed by an oxidative procedure. The reaction can utilize atmosphelic oxygen as the oxidizing agent. The crude aque- The peptide has now been converted to salmon calcitonin. The crude peptide solution obtained can be purified chromatographically to yield a freeze-dried product identical in chemical properties and biological activity to natural salmon calcitonin.

TYPE II PEPTIDE The Type II peptide contains a free thiol at cysteine position 1 and a S-n-alkylthio group at cysteine position 7. This peptide is converted to cyclic salmon calcitonin by the novel non-oxidative procedure set forth in our copending application Ser. No. 505,344. This method involves the rearrangement of disulfide bonds to form the internal disulfide bond in salmon calcitonin with the displacement of n-alkylmercaptan. This reaction is represented as follows:

H O pH 6.0 to 8.5

+ n-alkylmercaptan ous acetic acid solution of the peptide obtained from the HF cleavage may be diluted with distilled water to a volume of to 200 ml per gram of resin peptide cleaved. The pH of this solution may be raised from 6.0 to 8.5 by the addition of ammonium hydroxide solution. Air may be entrained into the solution for 2 to 20 hours or until no free thiol can be detected in the solu- TYPE III PEPTIDE The'Type III peptide contains a free thiol at cysteine position No. 7 and a S-n-alkylthio group at cysteine position No. 1. This peptide also may be converted to cyclic salmon calcitonin by the novel non-oxidative procedure set forth in our copending application Serv 10% triethylamine in chloroform for 5 minutes two times each Chloroform for 2 minutes Methylene chloride for 2 minutes three times each L S-S-n-alkyl ASNSERCi(S--NH H O pH 6.0 to 8.5

+ alkylmercaptan The reaction may be performed with either Type II or Type III peptides by diluting with distilled water the aqueous acetic acid solution of the crude Type 11 or III peptide from HF cleavage to a final volume of 50 to 200 ml per gram of resin peptide cleaved. The pH of this solution is adjusted to 6 to 9 by the addition of ammonium hydroxide solution and the mixture is stirred in a closed container under a stream of an inert gas such as nitrogen for 2 to 48 hours. The reaction period can be stopped when the off-gas stream no longer contains n-alkylmercaptan. The pH of the reaction mixture may be lowered to 3.5 to 5.5 by the addition of glacial acetic acid.

The peptide has now been converted to salmon calcitonin. The crude peptide solution obtained can be purified chromatographically to yield a freeze-dried product identical in chemical properties and biological activity to natural salmon calcitonin.

Purification of Crude Salmon Calcitonin The crude salmon calcitonin solutions at pH 5.0 from the above synthesis may be concentrated using an ionexchange procedure. The concentrate may be purified by a combination of gel-filtration procedures and ionexchange chromatography methods. The final purified product may be obtained from solution by freeze-drying as a fluffy white solid. This product will be found to be chemically and biologically equivalent to the product reported in literature (Guttman, S., et. al., Helv. Chim. Acta 52, 1789-95 [1969]). The product gives the correct amino acid analysis for salmon calcitonin.

Following are specific examples of the preparation of calcitonin in accordance with our procedures.

EXAMPLE 1 Resin Activation synthesizer marketed by Schwarz-Mann; 1116. of Orangeburg, New York. The resin was treated With 25 ml of the following solvents filtering after each treatment.

Methylene chloride for 2 minutes Chloroform for 2 minutes W0 times each CYCLE 32 Coupling: The BHA resin, 25 ml of methylene chloride and 1.29 g (0.006 moles) of BOC-L-proline was stirred for 10 minutes. 6.0 ml of a methylene chloride solution of dicyclohexylcarbodiimide (1 milliequivalent of DCCI per 1 ml of solution) was added to the reactor and the mixture agitated for 6 hours. The reaction mixture was removed from the reactor by filtration and the BOC-prolyl BHA resin subjected to the following successive 2 minute, 25 ml washes, removing the wash by filtration each time:

Methylene chloride two times Methyl alcohol two times Methylene chloride three times Acetylation: The resin was then agitated with a mixture of 1.5 ml of triethylamine (TEA), 1 ml of acetic anhydride and 25 ml of chloroform for 2 hours. The reaction mixture was removed by filtration and the resin subjected to the following 2 minute, 25 ml washes:

Chloroform two times Methyl alcohol two times Methylene chloride three times Deprotection: The BOC-protected resin was agitated for 5 minutes with a mixture of 15 ml of trifluoroacetic acid (TFA) and 15 ml of methylene chloride. This mixture was removed by filtration and the resin was agitated with a second mixture of 15 ml of TFA and 15 ml of methylene chloride for 30 minutes. The reaction mixture was removed by filtration and the resin subjected to the following 25 ml washes:

Methylene chloride two times two minutes each Methyl alcohol two times two minutes each Chloroform two times two minutes each 10% TBA in chloroform two times ten minutes each Chloroform two times two minutes each Methylene chloride two times two minutes each The L-proline BHA resin was titrated to establish the amine or proline titer. This value was 0.55 milliequivalents of amine or proline per gram of resin.

CYCLE 31 Coupling: The L-prolyl resin, 25 ml of methylene chloride and 1.7 g (0.0055 mole) of BOC-O-benzyl-L- threonine were agitated for minutes. Then 5.5 ml of a methylene chloride solution of dicyclohexylcarbodiimide (1 milliequivalent'of DCCI per 1 ml of solution or a total of 0.0055 mole of DCCI) was added to the reactor and the mixture agitated for 2 hours. The reac- 5 tion mixture was removed from the reactor and the resin was subjected to the following successive 2 minute, ml washes, removing the wash by filtration each time.

Methylene chloride two times Methyl alcohol two times Methylene chloride three times A ninhydrin test was negative.

Deprotection: The deprotection procedure described in Cycle 32 was repeated for this cycle.

CYCLES THROUGH 27 The coupling and deprotection procedures used in these cycles were the same as in Cycle 31 except that the following amino acid derivatives were used in place of the threonine derivative:

Cycle 30 0.97 g (0.0055 mole) of BOC-glycine Cycle 29 1.62 g (0.0055 mole) of BOC-O-Benzyl- L-serine Cycle 28 The material used was the same as Cycle 25 30. Cycle 27 The material used was the same as Cycle CYCLE 26 Coupling: The peptide resin obtained from Cycle 27 was washed twice with 25 ml portions of dimethylformamide (DMF). The resin was then agitated for 24 hours with a solution of 2.9 g (0.008 mole) of BOC-L- asparagine p-nitro-phenyl ester in 35 ml of DMF. The reaction mixture was filtered and the resin peptide subjected to two minute washes with two successive 25 ml portions of the following solvents: DMF, methylene chloride, methanol, methylene chloride. Each individual solvent was removed by filtration; A ninhydrin test was negative.

Deprotection: The deprotection procedure used in Cycle 32 was repeated.

CYCLE 25 Coupling and deprotection procedures were the same as in Cycle 31 using the same materials and amounts.

CYCLE 24 Coupling: The resin peptide obtained from Cycle 25 was washed with two successive 25 ml portions of DMF. The resin peptide was then agitated for 10 minutes with a mixture of 3.43 g (0.008 mole) of BOC-N- 'y-tosyl-L-arginine and 25 ml of DMF. Then 8 ml of DCCI in methylene chloride(equivalent to 0.008 mole of DCCI) was added and the mixture agitated for 6 hours. The reaction mixture was removed by filtration. The resin peptide was subjected to two minute washes with two successive 25 ml portions of the following solvents: DMF, methylene chloride, methyl alcohol, methylene chloride. The ninhydrin test was negative.

Deprotection: Repeat deprotection procedures used in Cycle 32.

CYCLE 23 Coupling: The peptide resin obtained from Cycle 24 was agitated for 10 minutes with 1.77 g (0.008 mole) of BOC-L-proline and 25 ml of methylene chloride. 8 ml of DCCl in methylene chloride (equivalent to 0.008 mole of DCCI) was added and the mixture agitated for 6 hours. The reaction mixture was removed by filtration and the resin peptide subjected to two minute washes with two successive 25 ml portions of the following solvents: methylene chloride, methyl alcohol, methylene chloride. Each individual wash was removed by filtration. The ninhydrin test was negative.

Deprotection: The deprotection procedure used in Cycle 32 was repeated.

CYCLES 22 AND 21 The coupling and deprotection procedures used in these cycles were the same as in Cycle 24 except that in the coupling reaction the following amino acid derivatives were used in place of BOC-L-proline.

Cycle 22 2.97 g (0.008 mole) of BOC-O-benzyl-L- tyrosine Cycle 21 ---2.47 g"(0.008 mole) of BOC-O-benzyl-L- threonine.

CYCLE 20 This procedure is the same as Cycle 26 except that 3.0 g (0.008 mole) of BOC-L-glutamine p-nitrophenyl ester is used in place of the asparagine derivative.

CYCLES 19 THROUGH 15 The procedure is the same as used in Cycle 31 except i that the following amino acid derivatives were used in place of the threonine derivative:

Cycle 19 1.37 g (0.0055 mole) of BOC-L-leucine Cycle 18 2.09 g (0.0055 mole) of BOC-s-carbobenzyloxy-L-lysine Cycle 17 2.58 g (0.0055 mole) of BCC-N(im)'-carbobenzyloxy-L-histidine Cycle 16 See Cycle 19 Cycle 15 1.85 g (0.0055 mole) of BOC-L-glutamic acid y-benzyl ester CYCLE 14 Same as Cycle 20 CYCLE 13 The procedure used was the same as used in Cycle 23 except that in the coupling reaction 2.36g (0.008 mole) of BOC-O-benzyl-L-serine was used in place of the proline derivative.

CYCLE 12 THROUGH 9 The procedures used were the same as used in Cycle 31 except in the coupling reactions the following amino acid derivatives were used in place of the threonine derivative.

Cycle 12 Same material as used in Cycle .19

Cycle 11 The material used was the same as in Cycle 18 Cycle 10 Same material as used in Cycle 30 Cycle 9 Same material as used in Cycle 19 CYCLE s Coupling: The resin peptide from Cycle 9 was agitated for 10 minutes with 1.79g (0.008 mole) of BOC- L-valine and 25 ml of methylene chloride. Then 8 ml of DCCI in methylene chloride (equivalent to 0.008 mole of DCCI) was added and the mixture agitated for 16 hours. The reaction mixture was removed by filtration.

The resin peptide was subjected to two minute washes with two successive 25 ml portions of the following solvents: methylene chloride, methyl alcohol, methylene chloride. Each individual wash was removed by filtration.

Deprotection: See Cycle 32.

CYCLE 7 The procedure was the same as used in Cycle 31 except that in the coupling reaction 1.55g (0.0055 mole) of BOC-S-ethylthio-L-cysteine was used in place of the threonine derivative.

CYCLE 6 The materials and procedures used were the same as Cycle 31.

CYCLE The materials and procedures used were the same as Cycle 29.

CYCLE 4 The materials and procedures used were the same as Cycle 19.

CYCLE 3 The materials and procedures used were the same as Cycle 26.

CYCLE 2 The materials and procedures used were the same as Cycle 29.

CYCLE l The procedures used were the same as used in Cycle 31 except that 1.88g (0.0055 mole) of BOC-S-pmethoxybenzyl-L-cysteine was used in place of the threonine derivative.

After completion of Cycle 1 the resin peptide was washed with two successive 25 ml portions of n-hexane. The peptide material was removed from the reactor and dried in an electric vacuum oven at 40C and 0.1 mm of Hg for 24 hours.

Cleavage with Hydrogen Fluoride Cyclization of Peptide to Salmon Calcitonin The aqueous acetic acid extract obtained from hydrogen fluoride cleavage was diluted to 1.5 liters by addition of 700 ml of distilled water. The pH of the solution was adjusted to 7.5 by the addition of concentrated ammonium hydroxide. The solution was stirred in a closed vessel under a stream of nitrogen for 24 hours. At this time no ethyl mercaptan could be detected in the emerging nitrogen stream. The ethyl mercaptan content of the nitrogen stream was measured by passing the stream through a solution of Ellmans reagent (Ellman, G. L., Arch. Biochem. Biophys., 82 -7 1959). The pH of the reaction mixture was adjusted to 5.0 by addition of glacial acetic acid.

Purification of the Crude Salmon Calcitonin The 1.5 liters of solution from the above synthesis at pH 5.0 was concentrated using a SP-Sephadex C-25 ion-exchange column. The ml concentrate removed from the column with 0.5 molar sodium chloride solution was desalted and purified by passing through a Sephadex G-25 (fine) gel-filtration column and eluting with 0.03 molar aqueous acetic acid solution. The salmon calcitonin fraction from this column was adjusted to pH 6.0 by addition of ammonium hydroxide solution. This solution was further purified by ion-exchange chromatography using a Whatman CM52 column eluted with ammonium acetate buffer. The salmon calcitonin fraction from this column was adjusted to pH 5.0 by addition of glacial acetic acid. This solution was concentrated using a SP-Sephadex C-25 ion-exchange column. The 30 ml concentrate removed from the column with 0.5 molar sodium chloride solution was desalted with a Sephadex G-25 (fine) gel-filtration column. The purified salmon calcitonin fraction was collected and freeze-dried. The product was obtained as a fluffy white solid. This material was found to be biologically and chemically equivalent to the product reported in literature (Guttmann, S., et.al., Helv. Chim. Acta 52, 1789-1795 [1969]).

The preparation of the compounds as heretofore described or as set forth in Example 1 may be varied in many respects, but when variations in more than one factor are made it is difficult to evaluate any one of the changed factors. For this reason we set up a series of tests in which only one factor is varied and the results compared.

EXAMPLE 2 EXAMPLE 3 The process set forth in Example 1 were repeated using the same materials, the same amounts, and the same conditions, except that in clcle 22 the BOC-O- benzyl-L-tyrosine was replaced with 3.45 g (0.008 mole) of BOC-O-2-bromobenzyloxycarbonyl-L-tyrosine. Results obtained were similar to that reported in Example 1.

EXAMPLE 4 All procedures, materials, and conditions were maintained the same as in Example 1 except that in cycles 18 and 11 the BOC-e-benzyloxycarbonyl-L-lysine was replaced at each of these cycles with 2.28 g (0.0055 mole) of BOC-e-Z-chlorobenzyloxycarbonyl-L-lysine.

Results were obtained substantially the same as in Example 1.

EXAMPLE 5 The materials, procedures, and conditions for the resin peptide synthesis may be used as in Example 1 21 except that in cycle 7 the BOC-S-ethy1thio-L-cysteine was replaced with 1.88 g (0.0055 mole) of BOC-S-pmethoxybenzyl-L-cysteine thus to prepare the Type I peptide.

The aqueous acetic acid extract obtained from the hydrofluoride cleavage may be diluted to 1.5 liters by addition of 800 ml of distilled water and the pH adjusted to 7.0 by the addition of concentrated ammonium hydroxide. A stream of air then may be entrained into the solution for a period of 8 hours. The pH of the reaction mixture may then be lowered to 5.0 by the addition of glacial acetic acid. Purification of the crude salmon calcitonin can be done in accordance with the same procedure as described in Example I.

EXAMPLE 6 All materials, procedures and conditions may be held to those of Example 1 except that in cycle 7 the BOC-S- ethylthio-L-cysteine be replaced with 1.48 g (0.0055 mole) of BOC-S-methylthio-L-cysteine.

Results may be expected similar to those obtained in Example 1.

EXAMPLE 7 All materials, procedures, and conditions may be held to those of Example 1 except that in cycle 1 the BOC-S-p-methoxybenzyl-L-cysteine be replaced by 1.66 g (0.0055 mole) of BOC-S-3,4-dimethylbenzyl-L- cysteine. We may expect results similar to those set forth in Example 1.

' EXAMPLE 8 All materials, procedures, and conditions may be held to those of Example 1 except for the following changes:

Cycle Change 1 Use 1.71 g. (0.0055 mole) of BOC-S-benzyl-L- cysteine in place of BOC-S-p-methoxybenzyl- L-cysteine.

7 Use 1.48 g (0.0055 mole) of BOC-S-methylthio- L-cysteine in place of BOC-S-ethylthio-L- Use 2.28 g (0.0055 mole) of BOC-e-Z-chlorobenzyloxycarbonyl-L-lysine in place of BOC-e-benzyloxycarbony1L-1ysine 18 Same as Cycle 11 above 22 Use 3.95 g (0.008 mole) of BOC-OQ-bromobenzyloxycarbonyl-L-tyrosine in place of BOC-O benzyl-L-tyrosine 24 Use 2.55 g (0.008 mole) of BOC-Q-nitro-L-arginine in place of BOC-N-y-tosyl-arginine Results similar to those of Example 1 would be expected.

EXAMPLE 9 All materials, procedures and conditions may be held to those of Example 1, except that in cycle 7 the amino acid derivative may be 1.88 g (0.0055 mole) of BOC-S- p-methoxybenzyl-L-cysteine and in cycle 1 the amino 22 intended that all such other embodiments and-changes be considered within the scope of the appended claims.

We claim: 1. A resin peptide having the structure 132 is s Nm-GLY-il-lR-PRO-NH H- where@ is divinylbenzene crosslinked polystyrene resin and B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4- chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or cycle 2. A resin peptide having the structure:

l T l NH HR-TYR-PRO-LRG- HRASNTHR-GLYI LIZ z ER-GLY THRPRONH H- where is divinylbenzene crosslinked polystyrene resin,

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-ch1orobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzy1, or benzhydryl,

W is BZ, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen,

and

T is nitro or tosyl.

3. A resin peptide having the structure:

Z Y -LEU-GLY LIS-LEU-SE R-GLN-ZLU-LEU-HlS- i2 82 i2 In, HR-GLY--LERGLY l-IR-PRO-NH H- where is divinylbenzene crosslinked polystyrene resin,

BZ is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl,

4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl, T is nitro or tosyl W is 82, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen, V is benzyloxycarbonyl, 2-bromobenzyloxycarbonyl or 2-chlorobenzyloxycarbonyl and one of R and R is an n-alkylthio and the other is BZ.

5. A resin peptide having the structure:

Z B2 B2 82 W BZ B2 82 cm,

GLYSER--GLYTHRPRO-NHCH- R B2 B2 BZ Z NH CiS LER-ASN-LEU-SER-THR-CYS-VAL LEU-GLY-LYS-LEU-SER GLN-LU-LEIJ-HIS-I I I l B2 B2 BZ cm,

THR GLYSERGLYTHR--PRO-NHCH- where is divinylbenzene crosslinked polystyrene resin,

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl,

T is nitro or tosyl,

W is BZ, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen,

V is benzyloxycarbonyl, 2-bromobenzyloxycarbonyl or 2chlorobenzyloxycarbonyl and R is an n-alkylthio group. 7. A peptide having the structure:

where R is an n-alkylthio group.

8. A peptide having the structure:

-THRGLYSERGLY -TH R-PRO-NH where R is an n-alkylthio group.

9. In a process for synthesizing salmon calcitonin, the step of mixing with the reactant BOC-glycine or an active ester, an azide or an anhydride thereof and unless said reactant is an active ester, an azide or an anhydride, in the presence of a diimide, to obtain where is divinylbenzene crosslinked polystyrene resm,

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl,

and

BOC is tertiary-butyloxycarbonyl.

10. In a process for synthesizing salmon calcitonin,

the step of mixing BZ BOC-NH-GLY-l'l-IR- PRONH with the reactant BOC-e-V-lysine or an active ester, an azide or an anhydride thereof and unless said reactant is an active ester, an azide or an anhydride, in the presence of a diimide, to obtain is divinylbenzene crosslinked polystyrene resin,

BZ is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlor0benzyl, 4-nitrobenzyl, or benzylhydryl,

T is nitro or tosyl,

W is 82, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen,

V is benzyloxycarbonyl, Z-bromobenzyloxycarbonyl or 2-chlorobenzyloxycarbonyl,

and v BOC is tertiary-butyloxycarbonyl.

11. In a process for synthesizing salmon calcitonin,

the step of mixing with the reactant BOC-R-L-cysteine or an active ester, an azide or an anhydride thereof and unless said reactant is an active ester, an azide or an anhydride, in the presence of a diimide, to obtain THR-PRO-NHCl-lwhere is divinylbenzene crosslinked polystyrene resin,

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl,

T is nitro or tosyl,

W is BZ, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen,

V is benzyloxycarbonyl, 2-bromobenzyloxycarbonyl or 2-chlorobenzyloxycarbonyl,

R is an n-alkylthio group and I BOC is tertiary-butyloxyc arbonyl. 12. In a process for synthesizing salmon calcitonin the step of mixing Z z MH -ZER-AsN-LEu IER-'iHR--cYs VAL-LEU- L BZ oLY LIs LEu iER oLN i i F with the reactant BOC-BZ-L-cysteine or an active ester, an azide or an anhydride thereof and unless said reactant is an active ester, an azide or an anhydride, in the presence of a diimide, to obtain i2 IZ I2 32 R BOC-NH- YS- ERASN EU-SERiHRCiS-VAL if, i l R- GLY- ERGLY HR-PRO-NHCH- BZ, T, W, V and BOC from said reaction product to obtain the structure:

14. In a process for synthesizing salmon calcitonin the step of mixing GLY-L S-LEU-lER-GLN- i GLY ER-GLY- HR-PRO-NH l-lwith the reactant BOC-R-L-cysteine or an active ester,

an azide or an anhydride thereof and unless said reactant is an active ester, an azide or an anhydride, in the presence of a diimide, to obtain BZ BZ CSHS z [THRGLYSERGLYTHR---PRONHCH where@ is divinylbenzene crosslinked polystyrene resin,

BZ is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chl0robenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl,

BZ, T, W, V, and BOC from said reaction product to obtain the structure:

-GLY-SER -GLYTHRPRONl-l 16. A process as set forth in claim 13 including the step of agitating the structure obtained by said cleaving step in a stream of inert gas to remove alkyl mercaptan with said gas and to join cysteine amino acid groups at positions I and 7 in a disulfide bond.

17. A process as set forth in claim 15 including the step of agitating the structure obtained by said cleaving step in a stream of inert gas to remove alkyl mercaptan with said gas and to join cysteine amino acid groups at positions 1 and 7 in a disulfide bond.

18. A process as set forth in claim 16 in which said gas is nitrogen.

19. A process as set forth in claim 17 in which said gas is nitrogen.

20. A process as set forth in claim 16 in which said agitation in a stream of inert gas is continued until alkyl mercaptan cannot be detected in said gas.

21. A process as set forth in claim 17 in which said agitation in a stream of inert gas is contained until alkyl mercaptan cannot be detected in said gas.

22. A resin peptide having the structure BOC-NH- GLYTHRPRO-NH H where@ is divinylbenzene crosslinked polystyrene resin,

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl,

and

BOC is tertiary-butyloxycarbonyl. 23. A resin peptide having the structure:

where is divinylbenzene crosslinked polystyrene resin, I

B2 is benzyl, 4-methoxybenzyl, 3,4-dimethylbenzyl, 4-chlorobenzyl, 2,6-dichlorobenzyl, 4-nitrobenzyl, or benzylhydryl, T is nitro or tosyl, W is BZ, benzyloxycarbonyl, 2-chlorobenzyloxycarbonyl, 2-bromobenzyloxycarbonyl or hydrogen, V is benzyloxycarbonyl, 2-bromobenzyloxycarbonyl or 2-chlorobenzyloxycarbonyl, BOC is tertiary-butyloxycarbonyl and one of R and R is an n-alkylthio and the other is BZ.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,926,938 Dated December 1975 lnventofls) John Lawrence Hughes et al. Page 1 of 5 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 11, line 1, the formula should show "C H attached by a bond line to "CHNH" and should show BZ attached by a bond line to THR, thus:

CHNH-PRO-THR- Column 18, line 17, "BOC-L-proline" should be BOC-g-tosyl-L-ARGININE Claim 5 in the last line of the formula beginning in line 2, a bond line should be placed between "THR" and GLY".

Claim 7, in the second line of the formula a bond line should be placed between "SER" AND "GLN", and in the last line of the formula a bond line should be placed between "THR" and "GLY".

Claim 9, a circle should be placed about "X" Claim 11, column 25, at lines 25-26, the end of the third line of the formula should be connected by a line to the UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent ,93 Dated December 16, 1975 Inventor( John Lawrence Hughes et al. Page 2 of 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

beginning of the last line of the formula.

Claim 12, in the formula beginning at column 25, line +5, the second line of the formula, "GLN" should be connected by a bond line to "GLU", and the third line of the formula should be joined by a line to the beginning of the last line of the formula.

Claim 15, the second formula should read as follows:

TYR-PRO-ARGTHR-ASNTHR-] NH CYS-SER-ASN-LE UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,926,938 Dated December 1975 John Lawrence Hughes et al. g 3 f 3 Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Claim 22. should read as follows:

A resin peptide .having the structure:

BZ C H BOC-NH-GLY-THR-PRO-NHCH- where@ is divinylbenzene crosslinked polystyrene resin B2 is beniyl, 4-methoxybenzyl, 3,4-dimethylbenzyl,

4,-chlorobenzyl, 2,6-dichlorobenzyl, i-nitrobenzyl,

or benzylhydryl,

and

ECG is tertiaryrbutyloxycarbonyl.

Claim 23 vthe end of line 1 of the formula should be joined by a line to the beginning of line 2 of the formula,

and line 3 of the formula should be joined by a line with the beginning of line i of the formula.

Signcd and Scaled this Twenty-sixth Day of October 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ojlatenrs and Trademarks o 

1. A resin peptide having the structure
 2. A resin peptide having the structure:
 3. A resin peptide having the structure:
 4. A resin peptide having the structure:
 5. A resin peptide having the structure:
 6. A resin peptide having the structure:
 7. A peptide having the structure:
 8. A peptide having the structure:
 9. In a process for synthesizing salmon calcitonin, the step of mixing
 10. In a process for synthesizing salmon calcitonin, the step of mixing
 11. In a process for synthesizing salmon calcitonin, the step of mixing
 12. IN A PROCESS FOR SYNTHESIZING SALMON CALCITONIN THE STEP OF MIXING
 13. A process as set forth in claim 12 including the step of treating the reaction product obtained in claim 12 with hydrogen fluoride to cleave
 14. In a process for synthesizing salmon calcitonin the step of mixing
 15. a process as set forth in claim 14 including the step of treating the reaction product of claim 14 with hydrogen fluoride to cleave
 16. A process as set forth in claim 13 including the step of agitating the structure obtained by said cleaving step in a stream of inert gas to remove alkyl mercaptan with said gas and to join cysteine amino acid groups at positions 1 and 7 in a disulfide bond.
 17. A process as set forth in claim 15 including the step of agitating the structure obtained by said cleaving step in a stream of inert gas to remove alkyl mercaptan with said gas and to join cysteine amino acid groups at positions 1 and 7 in a disulfide bond.
 18. A process as set forth in claim 16 in which said gas is nitrogen.
 19. A process as set forth in claim 17 in which said gas is nitrogen.
 20. A process as set forth in claim 16 in which said agitation in a stream of inert gas is continued until alkyl mercaptan cannot be detected in said gas.
 21. A process as set forth in claim 17 in which said agitation in a stream of inert gas is contained until alkyl mercaptan cannot be detected in said gas.
 22. A resin peptide having the structure BOC-NH-
 23. A resin peptide having the structure: 